How Does a Seat Belt Protect You in a Crash?

[dio11]

Homework Statement

In a test of a car seat belt system, a dummy of mass 55kg in a car seat is accelerated to a speed of 35m/s before it hits a brick wall. The seat belt allows the dummy to move forward relative to the seat by a distance of 0.60 m. Calculate,

(a) The deceleration of the dummy

(b) The force on the dummy due to the seat belt

Homework Equations

F=ma
F=p/t
F=mdv/dt

The Attempt at a Solution

I thought of using simultaneous equation to solve this. When I substituted the values to the equation F=ma, I realized F is an unknown. Then, time is also an unknown.

 

[ap123]

Hello dio11

If you assume that the acceleration is constant, then part (a) is a simple one-dimensional kinematics problem.